Field of the Invention
This invention concerns magnetic field transmitters, especially transmitters that are used in conjunction with wireless communications earplugs.
Description of Related Art
The inventor's co-pending U.S. patent application Ser. No. 11/837,129, entitled “Wireless Communications Headset System Employing a Loop Transmitter that Fits Around the Pinna” describes a loop transmitter comprising a coil of wire having an open center sized to fit around a pinna of a user's ear for use with communications earplugs. This invention is very effective in situations where there is limited volume available behind the human pinna such as when the transmitter is located in a shallow headset earcup or helmet, or other such applications, and the transmitter would otherwise be in contact with the pinna due to lack of space. However, larger transmitter coils are less efficient compared to smaller transmitters because they generate more unused magnetic flux. High efficiency transmitters are desirable in battery-operated devices because these devices would run longer on a single charge. Therefore, when space is available for a particular loop transmitter, it is desirable in many applications to employ a higher efficiency loop transmitter.